Stonewashing of cotton and cotton blend fabrics has gained great popularity and provides many styling applications in today's apparel market. This effect is chiefly applied to denim products but may be applied to cotton goods treated with vat, sulfur, reactive, direct and naphthol dyes, as well as pigments. Typically ring dyed yarns are woven and are then normally treated according to various so-called "stonewashing" processes that may or may not include abrasive materials to remove portions of the outer blue dyed yarns partially exposing the white portion of the yarn underneath. Stonewashing is costly and time consuming. The term "stone washing" and related descriptions herein refers to the use of abrasive stones such as pumice, cellulase enzymes or other treatments used to abrade fabrics or garments.
This invention provides an improved stonewashing effect while reducing or eliminating the use of abrasive materials by treating the ring dyed woven goods with a finish containing acid forming salts, solid organic acids, acid forming organic compounds, mineral acids or organic materials containing acid radicals, followed by drying, heating the goods to activate the acidic material, compressively shrinking and then cutting and sewing the garments followed by washing in garment form. The desired stonewashed look is achieved while saving one-third to one-half of the normal processing time and cost associated with conventional stonewashing.
The traditional procedure for providing a stonewashed appearance to garments is to expose the garment, typically denim jeans, to a combination of bleaching and an abrasive material. This combination provides a faded, worn appearance and is achieved by tumbling the garments with an abrasive substance, typically pumice stones and usually also with a bleaching solution such as potassium permanganate, a chlorine-based bleach or the like. Typically the garment to be stonewashed is denim or other type of cotton or a predominantly cotton garment in which the cotton yarn is ring dyed. When examined in cross section, the cotton fibers of the ring dyed yarn are dyed only around the outer circumference of the cotton yarn leaving the center portion or core undyed, hence the term "ring" when the yarns are viewed in cross section. Removal such as by abrasion or other means of a portion of the ring dyed outer surface of the yarn will leave the undyed portion exposed to view thus giving the faded appearance of a garment that has been worn for a considerable period of time. Abrasive treatment also imparts a worn, weathered appearance. In addition, the stonewashing process softens the hand of the garment giving it a more comfortable, less rigid, familiar feel and comfort when worn.
Conventional stonewashing procedures are time consuming and costly and provide garments which sometimes vary from batch to batch. In addition, stonewashing is usually performed on finished garments, that is garments in the completely constructed or fabricated condition. It would be desirable to provide a procedure that assures more uniform results prior to actual construction of the garment.
Several procedures have been proposed to achieve the appearance of stonewashed garments over shorter periods of time and/or at less cost. U.S. Pat. No. 4,816,033 describes a procedure for impregnating pumice rock with potassium permanganate solution under vacuum conditions, then tumbling the impregnated pumice rock with the garments to be stonewashed followed by neutralization, rinsing and drying. This procedure results in granules of pumice in the treatment and rinse water and also granules of pumice in the pockets and compartments of the constructed garments so treated.
A similar procedure for achieving a stonewashed look is described in U.S. Pat. No. 4,740,231 in which pumice granules are impregnated with a bleaching agent such as sodium hypochlorite. According to this disclosure the combined abrasive action from the pumice coupled with the bleaching action from the sodium hypochlorite reduces the processing time required to achieve the desired stonewashed appearance.
A difficulty with the use of pumice stones is that they average in size from 1 to 10 inches, often disintegrate into smaller size pieces and tend to accumulate in the pockets, interior closed or partially closed compartments and in the creases and folds of finished garments subjected to stonewashing. In addition, pumice powder tends to cause mechanical damage to the processing equipment and drive machinery, clogs drains and sewer lines and presents a sewage disposal problem for the finisher.
Chemical means without the use of abrasives to achieve the same or similar results have also been proposed. For example, U.S. Pat. No. 5,006,126 describes the use of cellulase enzyme to degrade or partially degrade the cellulosic fabric and release the dye from the fabric to achieve the stonewashed appearance with variations in local color density in fabric panels and seams of dyed cotton fabrics, especially denim.
A streaked, faded, worn appearance for denim is achieved according to U.S. Pat. No. 4,852,990 using a thickened/viscous aqueous solution of a chlorine bleaching agent in a polyacrylic acid. A similar procedure is described in U.K. patent application 2,213,842 A1 in which a fabric, typically denim, is decolorized selectively with a decolorizing paste to form patterns, characters or designs in the fabric followed by washing.
Published European application 0 404 009 describes the use of a dichloroisocyanuric acid salt as a decolorizing and bleaching agent for indigo fabrics.
Laid Open Japanese patent application 161,580/1991 describes a procedure for achieving a washed, worn-out appearance for cellulosic textile fabrics by applying a resin such as a cellulose reactive-type resin. The fabric is next scoured and bleached then subsequently dyed. The resin applied to the fabric acts as a dye resist, the areas of the fabric where the resin is present preventing the dye from entering and dyeing the cellulosic fabric resulting in a mottle dyed, washed and worn appearance.
Direct abrasion of denim fabric to achieve a softened, worn or laundered appearance with a stream of abrasive particles is described and illustrated in U.S. Pat. No. 4,951,366. The procedure is similar to that of sandblasting and the results achieved are said to resemble stonewashing.
The present invention achieves the desired worn, stonewashed appearance for denim and other types of cellulosic fabrics that are ring dyed by providing a controlled modification of the surface of the yarn, fabric, and/or dye such that further processing, for instance with strong bleaching agents, abrasive agents and the like or both, will result in the desired level of abrasion and stonewashed fabric appearance in a shorter period of time or at a reduced cost or, preferably, both.